Sahara as of 1970 had so low a level of urbanization that its period of major transformation still lies ahead of it; at the other extreme, Latin America already has nearly half its population in urban places; and the great populations of Asia are intermediate. If we take 70 percent as the standard for developed regions (excluding Oceania), then by the end of this century only Latin America has a chance of reaching this level, but Asia and Africa may be close to 50 percent.
The same pattern is seen when the city (a place of 100,000 or over) population is examined. (See Table 3.) The relative positions of Latin America, Asia, and Africa are the same.
It is characteristic of the urbanization process that, the more it progresses, the more significant the part represented by large urban places among the total urban population. Even now the developing world contains many of the world's largest urban centers. Shanghai, Sao Paulo, Peking, Mexico City, Calcutta, and Rio de Janeiro all have estimated 1970 populations of over 7 million. By 2000 the world's largest urban agglomeration will very probably be in a now-developing country.
Table 3 does not show the rate of growth of the population as a whole nor the absolute sizes of urban populations. In Africa for the period 1950-1970 the percentage increase of the urban population was 177; for Latin America, 136; for Asia, 135. By contrast, in Europe the gain in urban percentage was only 39, even though the proportionate increase was slightly higher than for Africa. The explanation is, of course, that Africa had a much higher rate of total population growth. It is also due to the rate of change of the rural populations. In the developed regions of the world, from 1960 to 1970 the rural population declined in absolute terms; in a number of developing regions rural growth exceeded 2 percent per annum.
Since the rate of urbanization in a country can vary only between the known limits of 0 and 100 percent, in the life span of any given country the period of intense urbanization during which the society is transformed from a primarily rural to a primarily urban one occupies a comparatively short time span. The peculiar problems that are associated with rapid urbanization are not permanent features in the history of a society. It is this feature of urbanization that gives a sense of urgency to efforts to affect and to guide the urbanization process. Many developing countries are now in the most critical period, and others are now on the threshold, of this transformation.
The Tempo of Urbanization
Urbanization is always the product of a unique historical development. Once the pattern is laid down it is usually very difficult to alter. Once begun, urbanization goes forward; a country becomes progressively more urban. (The few exceptions to this rule involve the breakdown of the social order, aswith an increase in the number of school-aee children, the sovern-oer caoita costs of sovern-shine returns: it would notelated collective consumption needs would stay largely unchanged for the better part of a decade, and